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Forgive me if this is addressed in a later edition, as I have read BTZS 2nd ed cover to cover, but only today found out there is a Beyond-BTZS (4th ed, even!).....
In the second edition, discussing the construction of the WonderWheel, Davis says that in the *first* edition, he "recommended calculating the exposure correction from the middensity level of the characteristic curves under the mistaken assumption that this would be appropriate when the center line of the fan is used as an exposure reference line."
I'm wondering first, what the method given in the first edition was (how was exposure correction based on mid-density actually implemented), and second, I'm interested in this whole concept. (And third, what was wrong with the 1st ed approach, specifically?)
In confession, it has actually always bothered me that meters read a mid-density (mid-tone/middle gray/etc), but we base the entire system on speed determined at the toe of the curve. (And further, when dealing with reversal materials, we *still* base the speed on the toe of the curve.)
I understand that we are definitely concerned with loosing detail in the unrecoverable area below base+fog, and thus speed determined on the toe represents a sort of worst-case. But it still seems unsatisfying to do it that way, particularly as the result says nothing about relative distance from mid- to toe versus mid- to shoulder.
Further, I can sort of understand desiring negs that are effectively as "thin as possible, but no thinner" (to turn a phrase from someone famous), but I'm wondering if working with super-dense negs might not be more advantageous in certain situations, such as when the "enlarging equipment" is actually a PMT-based drum scanner....
Anyway, I'm interested in thoughts on this subject! (And yes, I just ordered BTZS4ed!)
-frank
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